Add type annotations

[alexchandel]

Type checkers like mypy and Pylance have become ubiquitous in modern Python for quickly writing safe, bug-free code. They catch bugs coming from obscure corner cases that programmers often overlook. Without annotations, they often attempt to infer the signatures of functions.

However, there are come cases where type checkers are unable to infer them, including in graphviz, for example here:

import graphviz

dot = graphviz.Digraph(comment='Foo', format='png')

with dot.subgraph(name=f'cluster_Foo') as c:  # Object of type "None" cannot be used with "with"
    # these all work fine:
    c.attr(label='foo')
    c.attr(style='filled', color='lightgrey')
    c.node_attr.update(style='filled', color='white')
    c.node('bar')

Could you add type annotations for common functions and methods like Dot.subgraph() to disambiguate their signatures?